title: Ultrasound elastography in children: establishing the normal range of muscle elasticity.
abstract: BACKGROUND
  Ultrasound elastography allows assessment of tissue elasticity. To the best of our knowledge, the elastography appearance of muscles in normal children has not been described.
  
  
  OBJECTIVE
  To determine the US elasticity of muscles in children at rest and following exercise.
  
  
  METHODS
  Cine elastography of biceps brachii and rectus femoris muscles was obtained at rest and after exercise in 42 healthy children (23 males, 19 females; mean: 11.2 ± 4.4 years, range: 2-18 years). Elastography scores were assigned to each clip based on a five-point color scale. Mean elastography scores and standard deviations were calculated and resting and postexercise elastography scores were compared.
  
  
  RESULTS
  Resting muscle elasticity was lower in the biceps brachii than in the rectus femoris (P = 0.008), and higher in the dominant than in the nondominant biceps brachii (P < 0.032). Rectus femoris elasticity was higher in males than females (P = 0.051). Postexercise muscle elasticity significantly increased in both the dominant and nondominant biceps brachii (P < 0.001) and in the rectus femoris (P < 0.001). There was no significant gender-related difference in postexercise muscle elasticity. Biceps brachii elasticity decreased and rectus femoris elasticity increased with increasing body mass index. Younger subjects had a greater change in muscle elasticity with exercise.
  
  
  CONCLUSIONS
  Resting muscle elasticity in children is significantly lower in the biceps brachii than in the rectus femoris and in the nondominant biceps brachii than in the dominant biceps brachii. Elasticity significantly increases immediately postexercise in both muscle groups; resting differences between biceps brachii and rectus femoris elasticity, and dominant and nondominant biceps brachii elasticity, do not persist after exercise. The change in muscle elasticity with exercise is higher in younger children.
authors.affiliation: Department of Radiology, Montefiore Medical Center, 111 East 210th St., Bronx, NY, 10467, USA, nsberko@gmail.com.
authors.forename: Netanel S
authors.initials: NS
authors.lastname: Berko
authors.forename: Erin F
authors.initials: EF
authors.lastname: Fitzgerald
authors.forename: Terry D
authors.initials: TD
authors.lastname: Amaral
authors.forename: Monica
authors.initials: M
authors.lastname: Payares
authors.forename: Terry L
authors.initials: TL
authors.lastname: Levin
mesh_terms: D000293:Adolescent; D000375:Aging / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D055119:Elastic Modulus / Q000502:physiology; D054459:Elasticity Imaging Techniques / Q000592:standards*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging* / Q000502:physiology*; D009518:New York; D012016:Reference Values; D015203:Reproducibility of Results; D012146:Rest / Q000502:physiology; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical